Many of the conventional piezoelectric ceramic (piezoceramics) in mass production are configured from PZT (lead zirconate titanate) materials, and contain lead. In this connection, there is a need for the development of lead-free piezoceramics to eliminate the adverse effects of lead on the environment. For example, compositions represented by composition formula ANbO3 (A is an alkali metal), for example, potassium sodium niobate ((K,Na)NbO3), have been proposed as the materials of such lead-free piezoceramics (referred to as “lead-free piezoelectric ceramic composition”). However, the ANbO3 lead-free piezoelectric ceramic compositions themselves are problematic, because of poor sinterability and poor humidity resistance.
As a countermeasure against such problems, Patent Reference 1 discloses a method whereby copper (Cu), lithium (Li), tantalum (Ta), and the like are added to ANbO3 lead-free piezoelectric ceramic compositions to improve sinterability, and eventually, piezoelectric characteristics.
Patent Reference 2 discloses lead-free piezoelectric ceramic compositions of the general formula {Lix(K1-yNay)1-x}(Nb1-zSbz)O3 (0≦x≦0.2, 0≦y≦1.0, 0≦z≦0.2, excluding x=z=0) to achieve relatively desirable sinterability and piezoelectric characteristics.